Bearer of the curse, seek misery, Till this frail hope shatters. Lest this land swallow you whole.As it has so many others. The curse is a part of life itself.

Description

Your character in Dark Souls II is a cursed undead. Each playthrough starts with your character's full Humanity intact, but with each death a bit of Humanity is lost. This process is called "hollowing". Hollowing has several, mostly negative effects on gameplay:

Incremental reduction of your health bar with each in-game death (5% of max HP lost per death). Once your character is fully hollow, your available HP will be limited to 50% of max HP.

Restoring Humantity

Help other players in co-op kill bosses. Get summoned by placing a sign using the Small White Sign Soapstone or the White Sign Soapstone.
You don't need to actually kill the area boss in order to restore your Humanity if you complete your duty before a boss fight.